How far from greywater can I grow vegetables?

Gilbert Fritz

Posts: 1134

Location: Denver, CO

15

posted 3 weeks ago

I'm hoping to build greywater branched drain to mulch basin systems, following the directions in Art Ludwig's book. He strongly recommends NOT irrigating vegetables with greywater. I'm wondering how far back I should keep beds of annual or perennial vegetables from the greywater outfall. Any contact would be through the soil; no greywater would in any case splash or flow onto or into the vegetables.

Our system goes through a 3 part filter bed, starts with gravels then wetland grasses and finishes through a woodchip/oyster mushroom bed. Each of the filter beds is 5 feet long and 3 feet wide (we don't create much grey water since there are only two of us). The end of the filtering beds is a root vegetable garden, I tested the water outflow for 6 months and didn't ever see contaminants above 1ppm, at that point I stopped testing regularly and started watching the plants for indications of something going wrong. So far, after a year and a half, everything is still working great, we don't eat any of the oysters that fruit but we could, I just let them re-spore their area.

I have even used the spores of oyster mushrooms for the septic leach lines, and so far no contaminates are in the soil. Our septic system has been myco charged and bacterium charged on a monthly basis since we first acquired the land. The field lines are covered in sand, gravel and inoculated wood chips, 2 feet below soil surface and I test the soil in those areas monthly for pathogens. Our fruit trees are nearby and so far nothing is amiss.

For minimum distance I would add 5 feet to the furthest splash zone (I measured mine after doing a 10 foot pure water pour on bone dry soil, but I am perhaps overcautious because of my background in biology/ chemistry).
Our system comes out of a pipe that exits right at ground level, has three layers of 1/4 inch hardware cloth fastened over the end of the pipe to both keep critters out and to minimize any splashing outflow.

There is black & white. Pretty simple.
But, then there is grey. A million shades of grey between black & white.

To a certain extent, you can control which shade of grey you are producing.
Laundry detergents and soaps have varying degrees of 'earth friendlyness'.
Pick the greenest ones you can find...it's a step in the right direction.
Pre-soaking your clothes can remove much of the soil, therefore reducing the amount of detergent needed.

Gilbert Fritz wrote:Thanks for the advice, Bryant! What contaminants were you looking for? What types of soaps were going down the drain?

I test grey water for phosphates, chlorides and borates (boron can be found in some detergents without it being listed as such since it can be part of another compound and so not required to be listed)
We use fully biodegradable soaps, and very little of them, since Wolf prefers to hand wash our clothes and hang them on a line.
She had me build a two sink wash stand that sits outside and dumps directly into the filter bed system, everything except the black water is piped to the filter bed.

There is black & white. Pretty simple.
But, then there is grey. A million shades of grey between black & white.

To a certain extent, you can control which shade of grey you are producing.
Laundry detergents and soaps have varying degrees of 'earth friendlyness'.
Pick the greenest ones you can find...it's a step in the right direction.
Pre-soaking your clothes can remove much of the soil, therefore reducing the amount of detergent needed.

Indeed John, It is becoming pretty easy to find earth friendly products, but you do need to read the contents carefully.

We make our own detergent and use earth friendly, home made goat milk soaps.

Gilbert Fritz

Posts: 1134

Location: Denver, CO

15

posted 3 weeks ago

Thanks Bryant and John!

I'm planning on keeping the greywater a fairly light shade of grey; biodegradable soaps, and, in the particular system in question, no shower water.

What I was hoping is that by interspersing slightly raised vegetable beds with slightly sunken greywater tree basins, the vegetables could get their share of the water in a safe way. Sounds like this might be doable.